1. Field of the Invention
This invention relates to fail-safe anchoring systems for cavity walls. At the inner wythe, the anchoring systems provide a stud-type wall anchor with a hybrid connector portion for interlocking with a veneer anchor. The hybrid connector portion has two elements, namely, a thermoplastic portion and a metal stamping portion. Upon being subjected to a extreme heat or a fire, the thermoplastic portion is fail-prone and melts and the metal stamping portion is fail-safe and retains the veneer anchor. Under normal conditions, the thermoplastic portion provides a thermal break between the metal veneer anchor and the stud-type wall anchor.
2. Description of the Prior Art
In the past, anchoring systems have taken a variety of configurations. Where the applications included masonry backup walls, wall anchors were commonly incorporated into ladder- or truss-type reinforcements and provided wire-to-wire connections with box ties or pintle-receiving designs on the veneer side.
In the late 1980's, surface-mounted wall anchors were developed by Hohmann & Barnard, Inc., patented under U.S. Pat. No. 4,598,518 ('518). The invention was commercialized under trademarks DW-10®, DW-10-X®, and DW-10-HS®. These widely accepted building specialty products were designed primarily for drywall construction, but were also used with masonry backup walls. For seismic applications, it was common practice to use these wall anchors as part of the DW-10 Seismiclip® interlock system which added a Byna-Tie® wire formative, a Seismiclip® snap-in device—described in U.S. Pat. No. 4,875,319 ('319), and a continuous wire reinforcement.
In the dry wall application, the surface-mounted wall anchor of the above-described system has pronged legs that pierce the insulation and the wall board and rest against the metal stud to provide mechanical stability in a four-point landing arrangement. The vertical slot of the wall anchor enables the mason to have the wire tie adjustably positioned along a pathway of up to 3.625-inch (max). The interlock system served well and received high scores in testing and engineering evaluations which examined the effects of various forces, particularly lateral forces, upon brick veneer masonry construction. However, under certain conditions, the system did not sufficiently maintain the integrity of the insulation.
The engineering evaluations further described the advantages of having a continuous wire embedded in the mortar joint of anchored veneer wythes. The seismic aspects of these investigations were reported in the inventor's '319 patent. Besides earthquake protection, the failure of several high-rise buildings to withstand wind and other lateral forces resulted in the incorporation of a continuous wire reinforcement requirement in the Uniform Building Code provisions. The use of a continuous wire in masonry veneer walls has also been found to provide protection against problems arising from thermal expansion and contraction and to improve the uniformity of the distribution of lateral forces in the structure.
Shortly after the introduction of the pronged wall anchor, a seismic veneer anchor, which incorporated an L-shaped backplate, was introduced. This was formed from either 12- or 14-gauge sheetmetal and provided horizontally disposed openings in the arms thereof for pintle legs of the veneer anchor. In general, the pintle-receiving sheetmetal version of the Seismiclip® interlock system served well, but in addition to the insulation integrity problem, installations were hampered by mortar buildup interfering with pintle leg insertion.
In the late 1980's, an anchor for masonry veneer walls was developed and described in U.S. Pat. No. 4,764,069 by Reinwall et al., which patent is an improvement of the masonry veneer anchor of Lopez, U.S. Pat. No. 4,473,984. Here the anchors are keyed to elements that are installed using power-rotated drivers to deposit a mounting stud in a cementitious or masonry backup wall. Fittings are then attached to the stud which include an elongated eye and a wire tie therethrough for disposition in a bed joint of the outer wythe. It is instructive to note that pin-point loading—that is forces concentrated at substantially a single point—developed from this design configuration. Upon experiencing lateral forces over time, this resulted in the loosening of the stud.
Exemplary of the public sector building specification is that of the Energy Code Requirement, Boston, Mass. (See Chapter 13 of 780 CMR, Seventh Edition). This Code sets forth insulation R-values well in excess of prior editions and evokes an engineering response opting for thicker insulation and correspondingly larger cavities.
As insulation became thicker, the tearing of insulation during installation of the pronged DW-10X® wall anchor, see supra, became more prevalent. This occurred as the installer would fully insert one side of the wall anchor before seating the other side. The tearing would occur during the arcuate path of the insertion of the second leg. The gapping caused in the insulation permitted air and moisture to infiltrate through the insulation along the pathway formed by the tear. While the gapping was largely resolved by placing a self-sealing, dual-barrier polymeric membrane at the site of the legs and the mounting hardware, with increasing thickness in insulation, this patchwork became less desirable. The improvements hereinbelow in surface mounted wall anchors look toward greater retention of insulation integrity and less reliance on a patch.
In the past, the use of wire formatives have been limited by the mortar layer thickness which, in turn, are dictated either by the new building specifications or by pre-existing conditions, e.g. matching during renovations or additions to the existing mortar layer thickness. While arguments have been made for increasing the number of the fine-wire anchors per unit area of the facing layer, architects and architectural engineers have favored wire formative anchors of sturdier wire.
Contractors found that heavy wire anchors, with diameters approaching the mortar layer height specification, frequently result in misalignment. This led to the low-profile wall anchors of the inventors hereof as described in U.S. Pat. No. 6,279,283. However, the above-described technology did not fully address the adaption thereof to insulated inner wythes utilizing stabilized stud-type devices.
Another prior art development occurred shortly after that of Reinwall/Lopez when Hatzinikolas and Pacholok of Fero Holding Ltd. introduced their sheetmetal masonry connector for a cavity wall. This device is described in U.S. Pat. Nos. 5,392,581 and 4,869,043. Here a sheetmetal plate connects to the side of a dry wall column and protrudes through the insulation into the cavity. A wire tie is threaded through a slot in the leading edge of the plate capturing an insulative plate thereunder and extending into a bed joint of the veneer. The underlying sheetmetal plate is highly thermally conductive, and the '581 patent describes lowering the thermal conductivity by foraminously structuring the plate. However, as there is no thermal break or barrier, a concomitant loss of the insulative integrity results.
The construction of a steel-framed inner wythe of a commercial building, to which masonry veneer is attached, uses steel studs with insulation installed outboard of the steel stud framing. Steel anchors and ties attach the outer wythe to the inner wythe by screwing or bolting an anchor to a steel stud. Although steel offers many benefits, it does not provide the high insulation efficiency of timber framing and can cause the effective R-value of fiberglass batt insulation between the steel studs to fall 50 to 60%.
Steel is an extremely good conductor of heat. The use of steel anchors attached to steel framing draws heat from the inside of a building through the exterior sheathing and insulation, towards the exterior of the masonry wall. In order to maintain high insulation values, a thermal break or barrier is needed between the steel framing and the outer wythe. This is achieved by the present invention through the use of high-strength polymeric components which have low thermal conductivity. Removing the steel portions of the anchor at specific locations and replacing the steel with a high-strength polymeric material with a lower thermal conductivity than steel, causes a thermal break and significantly reduces the transfer of heat.
In the course of prosecution, wall anchor patents indicated by an asterisk on the tabulation below, came to the attention of the inventor and are believed to be relevant in this discussion of the prior art. A more extensive list of patents known to the inventor is included in the Information Disclosure Statement. Thereafter and in preparing for this disclosure, the additional patents which became known to the inventors are discussed further:
Pat.InventorIssue Date2,058,148*HardOct. 20, 19362,966,705*MasseyJan. 3, 19613,377,764StorchApr. 16, 19684,021,990*SchwalbergMay 10, 19774,305,239*GeraghtyDec. 15, 19814,373,314AllanFeb. 15, 19834,438,611*BryantMar. 27, 19844,473,984LopezOct. 2, 19844,598,518HohmannJul. 8, 19864,869,038CataniSep. 26, 19894,875,319HohmannOct. 24, 19895,392,581Hatzinikolas, et. al.Feb. 28, 19955,408,798HohmannApr. 25, 19955,456,052Anderson et al.Oct. 10, 19955,816,008HohmannOct. 6, 19986,209,281RiceApr. 3, 20016,279,283Hohmann et al.Aug. 28, 20017,415,803BronnerAug. 26, 20088,037,653Hohmann, Jr.Oct. 18, 2011
It is noted that with some exceptions these devices are generally descriptive of wire-to-wire anchors and wall ties and have various cooperative functional relationships with straight wire runs embedded in the inner and/or outer wythe.
U.S. Pat. No. 3,377,764—D. Storch—Issued Apr. 16, 1968 discloses a bent wire, tie-type anchor for embedment in a facing exterior wythe engaging with a loop attached to a straight wire run in a backup interior wythe.
U.S. Pat. No. 4,021,990—B. J. Schwalberg—Issued May 10, 1977 discloses a dry wall construction system for anchoring a facing veneer to wallboard/metal stud construction with a pronged sheetmetal anchor. Like Storch '764, the wall tie is embedded in the exterior wythe and is not attached to a straight wire run.
U.S. Pat. No. 4,373,314—J. A. Allan—Issued Feb. 15, 1983 discloses a vertical angle iron with one leg adapted for attachment to a stud and the other having elongated slots to accommodate wall ties. Insulation is applied between projecting vertical legs of adjacent angle irons with slots being spaced away from the stud to avoid the insulation.
U.S. Pat. No. 4,473,984—Lopez—Issued Oct. 2, 1984 discloses a curtain-wall masonry anchor system wherein a wall tie is attached to the inner wythe by a self-tapping screw to a metal stud and to the outer wythe by embedment in a corresponding bed joint. The stud is applied through a hole cut into the insulation.
U.S. Pat. No. 4,869,038—M. J. Catani—Issued Sep. 26, 1989 discloses a veneer wall anchor system having in the interior wythe a truss-type anchor, similar to Hala et al. '226, supra, but with horizontal sheetmetal extensions. The extensions are interlocked with bent wire pintle-type wall ties that are embedded within the exterior wythe.
U.S. Pat. No. 4,875,319—R. Hohmann—Issued Oct. 24, 1989 discloses a seismic construction system for anchoring a facing veneer to wallboard/metal stud construction with a pronged sheetmetal anchor. Wall tie is distinguished over that of Schwalberg '990 and is clipped onto a straight wire run.
U.S. Pat. No. 5,392,581—Hatzinikolas et al.—Issued Feb. 28, 1995 discloses a cavity-wall anchor having a conventional tie wire for mounting in the brick veneer and an L-shaped sheetmetal bracket for mounting vertically between side-by-side blocks and horizontally atop a course of blocks. The bracket has a slit which is vertically disposed and protrudes into the cavity. The slit provides for a vertically adjustable anchor.
U.S. Pat. No. 5,408,798—Hohmann—Issued Apr. 25, 1995 discloses a seismic construction system for a cavity wall having a masonry anchor, a wall tie, and a facing anchor. Sealed eye wires extend into the cavity and wire wall ties are threaded therethrough with the open ends thereof embedded with a Hohmann '319 (see supra) clip in the mortar layer of the brick veneer.
U.S. Pat. No. 5,456,052—Anderson et al.—Issued Oct. 10, 1995 discloses a two-part masonry brick tie, the first part being designed to be installed in the inner wythe and then, later when the brick veneer is erected to be interconnected by the second part. Both parts are constructed from sheetmetal and are arranged on substantially the same horizontal plane.
U.S. Pat. No. 5,816,008—Hohmann—Issued Oct. 6, 1998 discloses a brick veneer anchor primarily for use with a cavity wall with a drywall inner wythe. The device combines an L-shaped plate for mounting on the metal stud of the drywall and extending into the cavity with a T-head bent stay. After interengagement with the L-shaped plate the free end of the bent stay is embedded in the corresponding bed joint of the veneer.
U.S. Pat. No. 6,209,281—Rice—Issued Apr. 3, 2001 discloses a masonry anchor having a conventional tie wire for mounting in the brick veneer and sheetmetal bracket for mounting on the metal-stud-supported drywall. The bracket has a slit which is vertically disposed when the bracket is mounted on the metal stud and, in application, protrudes through the drywall into the cavity. The slit provides for a vertically adjustable anchor.
U.S. Pat. No. 6,279,283—Hohmann et al.—Issued Aug. 28, 2001 discloses a low-profile wall tie primarily for use in renovation construction where in order to match existing mortar height in the facing wythe a compressed wall tie is embedded in the bed joint of the brick veneer.
U.S. Pat. No. 7,415,803—Bronner—Issued Aug. 26, 2008 discloses a double-wingnut anchor system and method for connecting an anchor shaft extending from the backup wall to a wire tie extending from a veneer wall. The wingnut houses the wire tie legs and is independently rotatable to obtain the desired angular position.
U.S. Pat. No. 8,037,653—Hohmann, Jr.—Issued Oct. 18, 2011 discloses a dual seal anchoring system for insulated cavity walls. The stud anchor has a dual-diameter barrel with thermally-isolating seals.
None of the above provide the high-strength, supported stud-type wall anchor or anchoring systems utilizing these devices of this invention. As will become clear in reviewing the disclosure which follows, the cavity wall structures benefit from the recent developments described herein that lead to solving the problems of thermal conductivity by providing an in-cavity thermal break and of anchor integrity by having a hybrid wall anchor with both a failure-prone and a fail-safe receptor portions. The anchoring systems hereof combine various wall anchors for self-leveling installation and include reinforcement for seismic protection.